Diesel engines utilize compression ignition and an electrically heated glow plug to assist in starting, especially in cold weather conditions. Typically, a voltage is applied to the glow plug for a predetermined time to assist with compression starting by providing a hot spot near the fuel injector spray plume. To reduce the wait time for the glow plug to heat up to a temperature conducive for combustion to start an engine, a fixed higher voltage may be initially applied for a fixed time to reach a target temperature and then reduced to a fixed lower voltage to maintain the temperature.
The inventor herein has recognized that applying the higher voltage, typically 11 volts, even for a short time reduces glow plug life. This is especially true in the case of metallic, rather than ceramic, glow plugs. And, using lower voltages may result in unacceptably long start times. The inventor has solved these problems by controlling a first phase voltage having an amplitude related to a parameter associated with engine start time, and coupling a lower second phase voltage to the glow plug after the first phase voltage. In another aspect of the solution, the parameter is selected from one or more of the following: expected temperature of the glow plug during the second phase voltage, or the second phase voltage; or engine temperature. In yet another aspect of the solution, the time indicated for starting the engine, may also be related to these parameters.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.